Atrial fibrillation is a form of cardiac arrhythmia where there is disorganized electrical conduction in the atria causing rapid uncoordinated contractions that result in ineffective pumping of blood into the ventricle and a lack of synchrony. During atrial fibrillation, the atrioventricular node receives electrical impulses from numerous locations throughout the atria instead of only from the sinus node. This overwhelms the atrioventricular node into producing an irregular and rapid heartbeat. As a result, blood may pool in the atria increasing the risk for blood clot formation. The major risk factors for atrial fibrillation include age, coronary artery disease, rheumatic heart disease, hypertension, diabetes, and thyrotoxicosis. Atrial fibrillation affects 7% of the population over age 65.
Atrial fibrillation treatment options are somewhat limited. For instance, a lifestyle change only assists individuals with lifestyle related atrial fibrillation, and medication therapy assists only in the management of atrial fibrillation symptoms. In the latter, medication therapy may present side effects more dangerous than atrial fibrillation, and fail to cure atrial fibrillation. Electrical cardioversion attempts to restore sinus rhythm, even if successful acutely, often result in recurrence of atrial fibrillation. In addition, if there is a blood clot in the atria, cardioversion may cause the clot to leave the heart and travel to the brain (leading to stroke) or to some other part of the body.
One of the more recent procedures for treating cardiac arrhythmias is catheter ablation therapy. Physicians make use of specialized ablation catheters to gain access into interior regions of the body. Catheters with tip electrodes or other ablating devices are used to create ablation lesions that physiologically alter the ablated tissue without removal thereof, and thereby disrupt and/or block electrical pathways through the targeted tissue. In the treatment of cardiac arrhythmias, a specific area of cardiac tissue having aberrant electrically conductive pathways, such as atrial rotors, emitting or conducting erratic electrical impulses, is initially localized. A user (e.g., a physician) directs a catheter through a main vein or artery into the interior region of the heart that is to be treated. The ablating element or elements are next placed near the targeted cardiac tissue that is to be ablated, such as a pulmonary vein ostium or atrum.
While the currently available methods and devices for catheter ablation therapy are becoming more widely adopted, certain forms of atrial fibrillation, such as recurrent atrial fibrillation, and in particular, continuous atrial fibrillation, are considered very difficult to effectively treat applying this technique. Any patient with two or more identified episodes of atrial fibrillation is said to have recurrent atrial fibrillation.
Currently, the most common ablation catheter applied to treat continuous atrial fibrillation is a single-point tip-electrode ablation catheter that forms single-point ablation lesion. Such a catheter-based ablation therapy using single-point tip ablation catheters have shown only limited success, and proven tedious, extremely difficult to use, time-consuming, and often ineffective and impractical. There is therefore a need for improved atrial ablation products and procedures that effectively and efficiently treat continuous atrial fibrillation in a safe manner.